Subscriber devices, such as, for example, cellular radiotelephones, utilize units (e.g., airtime minutes or amounts of data) during usage of network services. Some network services permit the subscriber to pre-pay for service units, such as, for example, pre-paying for a certain number of minutes (e.g., 200 minutes) or a certain amount of data transfer (e.g., 50 Megabytes). After the subscriber uses up the pre-paid quota, the subscriber must pre-pay for additional service units to continue using the network services. Other network services permit the subscriber to post-pay for the service. In such cases, the subscriber may pay a flat fee for usage of service units up to a maximum amount, and then pay additional fees for usage of service units (i.e., per additional service unit) beyond the maximum amount for their selected payment plan. In both pre-pay and post-pay service usage, knowledge of a given subscriber's current “used units” or “remaining units” can be beneficial to the subscriber to enable the subscriber to ration their remaining usage of the service units. Currently, there exists no mechanism that permits a subscriber to monitor their service unit usage in real-time such that they can obtain an accurate accounting of their service unit usage at any given moment.